The proliferation of hematopoietic stem and progenitor cells in vivo is probably regulated by the colony stimulating factors (CSFs): interleukin-3 (IL-3) granulocyte-macrophage (GM)-CSF, granulocyte (G)-CSF, macrophage-CSF (CSF-1) and lactoferrin (LF). We will assess the production and action of CFSs. The aims are to: 1) Investigate actions in vivo of low dosages of endotoxin- free purified preparations of recombinant (r) murine IL-3, r murine GM-CSF, r human G-CSF and murine CSF-1 alone and in combination. Myelopoiesis will be evaluated in normal mice, mice pretreated with LF, mice recovering from treatment with cyclophosphamide or 5-fluorouracil, and mice infected with the polycythemia inducing strain of the Friend Virus Complex. Mice will be assessed for bone marrow, spleen and peripheral blood counts and differentials, hematopoietic progenitors (CFU-GM, mature and "immature" BFU-E, CFU-GEMM, HPP-CFC) and stem(s) cells per femur and spleen, the cycling status of these cells, self-renewal (replating) capacity of S-cells, and serum concentrations of IL-3, GM-CSF, G-CSF, CSF-1, IL-1, interferon IFN)- gamma and -alpha, prostaglandin E (PGE), acidic isoferritins (AIF) and tumor necrosis factor (TNF). 2) Determine the influence in vitro of murine and human CSFs (IL-3, GM-CSF, G- CSF, CSF-1) and human LF alone and in combination on production and release of CSFs, IL-1, AIF, PGE, IFN-gamma, IFN- alpha, and TNF from murine or human monocytes-macrophages, T-lymphocytes or fibroblasts with and without serum. This will entail: a. assessing effects on populations and subpopulations of cells within a lineage using cells separated with antibodies to subpopulation lineage antigens, and also cells expressing different densities of major histocompatibility class II antigens, b. correlating receptor-binding, gene expression for IL-3, GM-CSF, G-CSF, CSF-1, IL-1 alpha, IL-1 beta and release of biologically active molecules, c. characterizing differences between LF isolated from PMN of normal donors and patients with Chronic Myelogenous Leukemia by biochemical (iron-binding, carbohydrate, structural) and functional (receptor binding and mononuclear cell gene expression and release of IL-1, GM-CSF or G-CSF) analysis. These studies should help to evaluate the relevance of CSFs and LF and how they regulate myelopoiesis.